Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment

Definitions

• This invention relates to the application of a pigment to oxidized surfaces of aluminum.
• aluminum as used herein, is meant. to include aluminum alloys as well as commercially pure aluminum.
• This invention relates more particularly to the application of a black, cobalt pigment to anodized alumium.
• a black pigment for example, it is known to apply a black pigment to anodized aluminum by soaking an aluminum article having an anodized surface in a bath of cobalt acetate, rinsing and then subjecting the article to the action of an aqueous bath of ammonium sulfide. The article is then rinsed and subjected to the action of hot water to seal the anodized aluminum, that is, to make it less porous.
• such practice produces various shades of black from one lot to another, and even in a single lot or on a single metal article.
• I provide an aluminum article or articles having an oxide coating of a type which will adsorb or absorb a color material, for
• a dye stuif such. as an azo dye, or an inorganic pigment such as the cobalt sulfide pigment hereinafter described. 7 I
• anodized aluminum that is to say, aluminum to which an oxide coating has been applied by anodic oxidation.
• Such anodizing processes are well known and do not require detailed description herein.
• a sulfuric acid solution as the electrolyte, or to employ a chromic acid solu-
• the aluminum article is made the anode and current is passed through the bath to form a thin, dense coating of alumi-.1
• oxide coating on the metal As is well known in the art, it is a common practice to seal such an oxide coating by treatment with hot water, the reason being that oxide coatings formed in this manner tend to be rather porous and it is preferred to render them nonporous.
• the oxide coating may be applied by any desired method that will produce an oxide .that will absorb the coloring agent, preferably by anodizing.
• the application of pigment is preferably done before the final sealing step.
• Various cobalt salts may be used, one of the best being cobaltous acetate. Any other soluble cobalt salt in which the cobalt is in the form of its cation which is soluble in water, may be used.
• cobalt salts of other carboxylic acids may be used such as cobaltous benzoate, cobaltous propionate, cobaltous formate, cobaltous bromate, cobaltous chlorate, cobaltous chloride, cobaltous fluosilicate, cobaltous nitrate and cobaltous sulfate.
• certain of these salts are less desirable than others.
• the chloride is less desirable because it has a tendency to pit aluminum.
• all soluble cobaltsalts may be used which, upon addition of a sulfide, precipitate a black cobalt sulfide.
• the aluminum article to be treated is soaked in an aqueous bath of cobalt salt, e.g., 5 to 15 minutes at room temperature sufiicient to deposit the cobalt salt in the oxide film.
• a nitrogen-containing control agent e.g., sulfamic acid, but others may be used, for example, glycine, ammonium nitrate, ammonia. and triethanolamine.
• control agent may vary considerably; e.g., it may be present in the amount of 1% or less to 20% or more, preferably about 2 to 15% based on the weight of solution of cobalt salt.
• the article After soaking in this bath, the article is removed and preferably rinsed with water. Then it is soaked, e.g., 1 to 12 minutes at room temperature in an aqueous bath of a soluble sulfide, e.g., ammonium sulfide of 3 to 20% concentration. Then the article is removed and rinsed and the oxide surface is sealed by any suitable means, e.g., by immersing it in hot water.
• a soluble sulfide e.g., ammonium sulfide of 3 to 20% concentration.
• a sheet of aluminum alloy of the type 6063 was anodized to produce a layer of oxide film about 0.001" thick.
• the anodizing was carried out in a bath of 15% sulfuric acid by placing thealuminum sheet in the bath,
• concentrations of the various reactants (colorforrning metal'salt and precipitant) and control agents may vary widely.
• the color-forming salt maybe used from a 2% concentration up to saturation, about 10 to 20% being usually preferred.
• a process of applying a metal sulfide pigment to anodized aluminum comprising:' providing a body of aluminum having an anodized, unsealed surface; sub-- jecti'ng such surface to contact With a first aqueous solution of a soluble 'salt of a metal cation selected from the group consisting of cobalt, lead, copper and silver of said solution and being selected from the group consisting of'sulfamic acid, glycine, triethanolamine, am-

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (3)

Cited By (9)

Citations (5)

• 0
  • NL NL124780D patent/NL124780C/xx active
  • NL NL283883D patent/NL283883A/xx unknown
• 1961
  • 1961-10-03 US US142478A patent/US3152970A/en not_active Expired - Lifetime
• 1962
  • 1962-10-02 GB GB37266/62A patent/GB995923A/en not_active Expired

Patent Citations (5)

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